This invention relates to liposomes having a bilayer composed of rhamnolipid A, rhamnolipid B or a salt thereof.
In 1965 Bangham discovered that phosphatidylcholine forms liposomes (vesicles) which are microscopic particles with a diameter of 0.05-10 .mu.m composed of biomembrane-like lipid bilayers. Thenceforth, a variety of studies have been made on applications of liposomes as a tool for studying the structures and functions of biological membranes, as a drug carrier for therapeutic purposes, and as a reaction medium for biological reactions. Liposomes have been also attempted to be used in the field of genetic engineering.
One problem associated with phosphatidylcholine liposomes is that they are unstable. That is, the liposomes are easily decomposed by heat or light and, therefore, they are susceptible to degradation during manufacture and storage. Further, the phospholipid liposomes are short in life and, therefore, they pose a particular difficulty of shelf conservation.
Liposomes formed of synthetic surfactants such as aerosol OT type anion dialkyl compounds and didodecylmethylammonium bromide are also known. However, these liposomes are not actually used for therapeutic or other applications for reasons of lack of safety, namely because of their skin irritating properties and their resistance to biological decomposition.